Stroke is the third leading cause of death among adults in the US and the leading cause of disability. The ability to use the wrist and hand to orient and grasp objects is at most risk in moderately impaired individuals such as those suffering the after effects of a stroke. To effectively use the impaired wrist and hand functionally, persons need the ability to position and stabilize the hand at appropriate spatial locations. This ability may be greatly impaired in a person who has suffered a stroke.
One important question that has not been addressed systematically in this population is how much of their inability to use the wrist and hand functionally is contributed by the inability to properly control and stabilize the arm posture versus specific difficulty in coordinating the wrist and hand muscles. If poor control of the arm posture has consequences for wrist and hand control, then the training of wrist/hand function should be facilitated by an intervention that assists with arm postural control.
Over the past several years, arm training devices have been developed to assist in rehabilitating patients who have suffered loss of arm movement, such as due to an injury or stroke. One such device is described in U.S. patent application Ser. No. 12/568,541, titled “UPPER ARM WEARABLE EXOSKELETON,” filed Sep. 26, 2009, incorporated herein by reference. Many prior devices, including the device described in the above-referenced patent application, have been limited in their capabilities due to their weight. For example, in one embodiment of the device described in the above-referenced patent application, a plurality of cables are driven by motors mounted to a shoulder cuff worn by the patient. The weight of the motors mounted to the shoulder cuff may add significant weight to a device for use with a patient who may already be in a somewhat weakened state. Accordingly, there exists a need to develop a device to assist and train arm movements of stroke survivors or subjects with weak musculature that can be worn by the user as an exoskeleton without providing a cumbersome amount of weight that will hinder the user's movement and rehabilitation process.